17

Most motors on quadcopters are outrunners. In outrunner motors, the rotating part is on the outside, and not the inside (as opposed to the inrunner motors). Because of this layout this type of motors can generate much more torque. High torque is required for quadcopters, since you balance by changing the revolutions of the motor. The higher your torque the ...


12

The diagram you show looks like it would produce a pretty rough trapezoidal Back-EMF. I'm assuming that the gates that are at 100% are the lower legs of the motor drive bridge. I can't think of a reason you would want to do this. In general you want the gate voltage of the return leg to be the complement of the gate voltage of the supply leg. In six-step ...


12

There is a fair deal of literature on the implementation of brushless motor control but here is an overview. To understand the differences between commutation waveforms it is important to understand how brushless motors operate. A three phase (two pole) motor will have three coils around a single magnet in the center. The goal is to energize the coils in ...


11

The brushless motors are way more powerful for their weight than available brushed motors, and they last longer. Power to weight ratio is king, in an aircraft.


7

Let's try and clear things up a little bit... "RC Servo" motors These can be found in radio controlled cars and airplanes to e.g. turn the wheel or actuate various controls in the airplane. They are pretty cheap brushed DC motors, with gears and some sort of crude feedback mechanism. They typically convert an input voltage into a position within a given ...


7

A couple things, the first is that the controller does not really care what the "real" values are. Everything is relative, if the controller sees that it is sinking it will increase the thrust until it is not sinking. If it is tilting too far to the left it will decrease the right thrust and increase the left thrust. (Here is a good resource if you want to ...


6

Brushed motors are easier for servo systems, but are not better. Many high end servo systems are brushless/AC. It is possible to control the motors at low speeds with only 3 hall sensors. You really don't want trapezoidal commutation, especially at low speeds so could add an encoder or estimate the rotor position if necessary. It is possible to estimate ...


6

I think the term you're looking for is outrunner (vs inrunner): This type of motor spins its outer shell around its windings [...] Outrunners spin much slower than their inrunner counterparts with their more traditional layout (though still considerably faster than ferrite motors) while producing far more torque. This makes an outrunner an ...


5

For the smallest (and cheapest) of multicopters, DC brushed motors are well in use: http://www.rcgroups.com/forums/showthread.php?t=2009496 They are coreless motors1 and have very little inertia, can accelerate very quickly and are perfectly suited for high frquency PWM (we drive them with up to 32kHz). You can achieve more than 3:1 power:weight ratio on a ...


5

Model Based: Low cost solution is always software: Develop a dynamic model which computes the load on the motors based on the motions (e.g. with Recursive Newton Euler Algorithm or Lagrange-Euler Method) Make as simple model to handle losses in driver/motor Make the difference between real torque and computed torque It will be not accurate. At least 10% ...


5

Your expectations are rather aggressive for a DC motor. First - 40Nm (350in-lbs) is A LOT of torque! Ex: A max rated torque for 1/4-20 bolt is only 75 in-lb (8.5Nm). Second - The mechanical power of a motor results from RPM*Torque. 40Nm*100rpm is 0.56hp (420W at 100% efficiency). That is A LOT, about 1/2 of what today's high end cordless drills can do. ...


4

In industry, there is a strong preference for low maintenance brush-less motors over relatively high maintenance brushed motors. While the former may me more expensive in terms of the motor itself and the drive electronics, the reduction in the term long cost of maintenance usually out weighs the extra capital cost. As user65 suggests, you may need ...


4

Brushless DC motors should have excellant lower speed performance. Your problem is probably not the motor but rather the electronic speed controller. Those sensorless controllers generally don't perform well in low speeds because there is very little signal for them to key on. It also sounds like you may be "fighting" the ESC's built in controller with ...


4

Each of the three Hall Effect sensor signals is out of phase with the others by 120°. The same is true for the BEMF signals. The Hall Effect signals and the BEMF signals are 30° out of phase with each other. From this Microchip App note: Hall sensor signals are out of phase by 120 degrees to each other. At every 60 degrees, one of the Hall sensors ...


3

In process of selection of components for multirotor, one should start from motor as it is the driving component. Maximum current drawn by your motor is given by manufacture which is 15A. Now your ESC should have maximum current rating more than maximum current rating of motor. This is satisfied in your motor-ESC combination so your selection looks good. ...


3

First, you can look at Mikrokopter as an example of quad with centrally mounted ESCs. As for the various engineering reasons for ESC location, here is some rationale behind the two you mentioned 1) Interference/noise. Non-steady state current running through wire can induce current to flow in nearby conductors. Practically speaking, this means that if you ...


3

I believe the most efficient thing to do is to maintain a 90 degree phase lead, and adjust your voltage magnitude for control. You'll probably want to have an inner current loop, wrapped by the actual position loop.


3

You can control brushless motors 2 ways control with a hall effect sensor http://scholar.lib.vt.edu/theses/available/etd-09152003-171904/unrestricted/T.pdf sensorless(back emf) control http://www.pmdcorp.com/downloads/app_notes/BrushlessSensorConfig.pdf or you can buy an esc (elcetronic speed control) My advice If you are not knowledgeable about electronic ...


3

Your equipment will be fine as long as the stall periods aren't too big(like 5 minutes). I think the first thing to fail is the ESC as you're using half the voltage the motor is rated for. You also have to take into account that the battery can also heat up and fail, as if you would short circuit the battery. But as I said, if it's not for long periods of ...


3

Page 7 of this PDF states that, "A permanent magnet DC brushless motor behaves like any permanent magnet DC brush motor." You can read more about DC motor operation at this MIT site. I'm not sure if you've got a typo or what you're trying to say, but your question states, "brushless motors decrease torque with speed," after you state that using a gearbox ...


3

You can't understand this because you don't know what you observe. The electromotive force (EMF) of your motor is proportional to its speed (the ratio is called Kv). So, when the speed of your motor rises, the EMF rises too. What does an ESC ? Basically, it hashes the input voltage to generate the expected output voltage. So, what is this decreasing ...


3

Okay I thought I'd move this to an answer because I think this will help clear up some confusion you have. First, if you are trying to plot RPM vs Thrust, then your battery, ESC, power, etc. have nothing to do with RPM vs Thrust, assuming the battery and ESC are sized correctly to provide adequate current to the motor. It's like saying you want to ...


3

I would definately look at brushed motor when the budget is low. They have a reputation of being less powerful but the main problem is they have a very high RPM. This means you either have to use very small inefficient propellers or a geared system. Brushed geared mini drones have pretty good performance when it comes to battery life because the propeller is ...


3

I took apart a Turnigy D2836 brushless DC motor. Despite the weight listed on the website, the actual weight of the motor without the mounting equipment is 54 Grams. Here is the breakdown Magnets: 9 grams, 16.7% Bottom Can: 6 grams, 11.1% Top Can: 4.5 grams, 8.33% Main Axle: 1.5 grams, 2.78% Middle can: 9 grams, 16.7% Coils: 6 grams, 11.1% Leads & ...


3

It depends on the voltage. Say you are running 12V: 1820W / 12V = 151A With a 24V system: 1820W / 24 = 75A


2

Sometimes they are called linear halls. A company called Eltrol used to make drives for these. I used them in the past in combination with Anorad Linear motors. Nowadays they are still available from PeakServo. The drives drive the linear (or sine) hall and receive the two halll signal (which are 120 degrees apart). http://www.peakservo.com/series-45-...


2

I'm reasonably sure that the sinusoidal wave will look like a sign wave, and that the trapezoidal wave will look more square-ish. The image below explains it better:


2

This is correct. Just make sure to insert a lever into the hole at the top to really tighten the nut!


2

One possible solution to your torque problem is to use mechanical advantage to trade speed for torque. If you replace a 1:2 gear/drive belt combination with a 1:1 gear/drive belt combination then you will get twice the torque at half the speed. Swap the gears and you can use the same drive belt to get a 2:1 ratio instead and get even more torque for even ...


2

Ian is absolutely right. I've been in the RC hobby for years. Your drivetrain/gearing is going to be your biggest factor into deciding inrunner vs. outrunner. You must also consider your power source and figure out it's voltage and max current output and be sure it has enough capacity (typically measured in milliamp/hours). To make things easier, I'd ...


Only top voted, non community-wiki answers of a minimum length are eligible